Answer: "The attack on Pearl Harbor on December 7, 1941, was a pivotal moment in American history that not only led to the United States' entry into World War II but also transformed the nation's political, economic, and social landscape, shaping the course of the 20th century."
Explanation: This thesis statement provides a broad overview of the significance of the Pearl Harbor attack and hints at several potential lines of inquiry for the research paper, including the immediate and long-term effects of the attack on the United States and its place in the world, the factors that led to the attack, and the political and social context of the time period.